New York City police have been searching for a woman who fled a Queens subway station after witnesses said she fatally pushed a man in front of an oncoming train.

At 8:04 p.m. on Thursday an unidentified man was standing on the elevated northbound platform at 40th Street and Queens Boulevard, waiting for the No. 7 train. Witnesses told police that a woman had been walking back and forth on the platform and talking to herself before she took a seat on a wooden bench on the platform.

As the No. 7 train approached the station, witnesses said the woman rose from the bench and pushed the man, who'd been standing with his back to her, onto the tracks.

Witnesses told police that the victim did not seem to notice the woman behind him. He was struck by the first of the 11-car train. His body was pinned under the front of the second car as the train came to a stop, according to a statement from Deputy Police Commissioner Paul Browne.

After pushing the man onto the platform, the woman fled down the stairs to Queens Boulevard. She was described as wearing a blue, white and gray ski jacket, and gray-and-red Nike sneakers.

The police said they had not found any connection between the victim and the attacker.

Overnight the New York Police Department released surveillance video of the woman believed to be the suspect, Detectives were also canvassing locations along Queens Boulevard for other witnesses and surveillance video.

On Friday, New York City Mayor Michael Bloomberg was asked whether the attack might be related to the increase of mentally ill people on the streets following closures of institutions over the past four decades.

"The courts or the law have changed and said, no, you can't do that unless they're a danger to society. Our laws protect you," Bloomberg said on his weekly radio show.